Anti-balling drill bit

Abstract

The invention concerns an anti-balling drill bit. The drill bit includes an approximately cylindrical steel body provided at one end with axial arms on which are mounted toothed conical wheels. The bottom of the tool body has a dome shaped profile such as a parabolic profile, whose flanks are joined at an apex located approximately along the axis (x--x) of the tool. The flanks ascend toward the cylindrical wall of the body through gaps between the arms with unbroken surfaces and without edges, each arm bearing at its end at least one extension nozzle for emitting a liquid jet, and nozzles also being mounted in said flanks.

We claim: 
     
       1. An earth boring drill bit, comprising: a bit body;   a plurality of cutter arms extending downwardly from said bit body, substantially parallel to a longitudinal axis of said bit body;   a plurality of gaps between said cutter arms, said gaps being free of any projecting element; and   a downwardly projecting smooth protuberance formed on a bottom surface of said bit body between said cutter arms, said protuberance having an apex located approximately on said longitudinal axis of said bit body, said protuberance having a plurality of side surfaces ascending from said apex toward an outer periphery of said bit body through said gaps, said protuberance forming an unbroken surface on said bottom of said bit body without any edges or obstacles to impede fluid flow, said side surfaces being transitioned into inwardly facing surfaces of said cutter arms via unbroken surfaces.   
     
     
       2. An earth boring drill bit according to claim 1, wherein said side surfaces of said protuberance are convex. 
     
     
       3. An earth boring drill bit according to claim 1, wherein said side surfaces of said protuberance are slightly concave. 
     
     
       4. An earth boring drill bit according to claim 1, further comprising: a plurality of nozzles fixed to said cutter arms so as to emit liquid jets; and   a plurality of conical cutter wheels mounted on said cutter arms;   wherein the axes of said cutter wheels are offset in an angular direction, each said nozzle being positioned on a side of its respective said cutter arm opposite from said direction of said angular offset of said cutter wheels.   
     
     
       5. An earth boring drill bit according to claim 1, further comprising a plurality of nozzles mounted in said side surfaces of said protuberance, said nozzles being mounted so as not to project beyond said side surfaces. 
     
     
       6. An earth boring drill bit, comprising: a bit body, said bit body being threaded at a first end and provided at a second end with a plurality of arms extending substantially parallel to a longitudinal axis of said bit body;   a plurality of conical cutter wheels mounted on said arms;   a dome-shaped profile formed on a bottom surface of said bit body between said arms, said domed profile having a contour selected from the group of parabolic, hemispherical and truncated contours;   a plurality of slanted surfaces on said domed profile, said slanted surfaces being joined together at an apex located approximately on said longitudinal axis of said bit body, said slanted surfaces ascending toward an outer periphery of said bit body through a plurality of gaps between said arms, forming an unbroken surface on said bottom surface of said bit body without any edges or obstacles to impede fluid flow;   at least one nozzle fixed to each arm so as to emit a liquid jet; and   a plurality of nozzles mounted in said slanted surfaces;   wherein said gaps are free of any projecting element; and   wherein said slanted surfaces are transitioned into interior surfaces of said arms via unbroken surfaces.   
     
     
       7. An earth boring drill bit according to claim 6, wherein said slanted surfaces are convex. 
     
     
       8. An earth boring drill bit according to claim 6, wherein said slanted surfaces are slightly concave. 
     
     
       9. An earth boring drill bit according to claim 6, wherein the axes of said cutter wheels are angularly offset from said longitudinal axis of said bit body, and wherein each nozzle fixed to one of said arms is positioned on a side of its respective said arm which is opposite the direction of the angular offset of its respective said cutter wheel. 
     
     
       10. An earth boring drill bit according to claim 6, wherein said nozzles mounted in said slanted surfaces do not project beyond said slanted surfaces. 
     
     
       11. An earth boring drill bit, comprising: a bit body, said bit body being substantially cylindrical near its upper end, said bit body having a plurality of indentations near its lower end;   a plurality of cutter arms extending downwardly from said bit body, substantially parallel to a longitudinal axis of said bit body;   a plurality of cutter arm nozzles fixed to said cutter arms so as to emit liquid jets;   a plurality of conical cutter wheels mounted on said cutter arms;   a plurality of gaps between said cutter arms, said gaps substantially aligning with said indentations in said bit body, said gaps being free of any projecting element;   a downwardly projecting smooth protuberance formed on a bottom surface of said bit body between said cutter arms, said protuberance having an apex located approximately on said longitudinal axis of said bit body, said protuberance having a plurality of side surfaces ascending from said apex toward an outer periphery of said bit body through said gaps, said protuberance forming an unbroken surface on said bottom of said bit body without any edges or obstacles to impede fluid flow, said side surfaces being transitioned into inwardly facing surfaces of said cutter arms via unbroken surfaces;   a plurality of side surface nozzles mounted in said side surfaces of said protuberance, said side surface nozzles being mounted so as not to project beyond said side surfaces of said protuberance.   
     
     
       12. An earth boring drill bit according to claim 11, wherein said side surfaces of said protuberance are convex. 
     
     
       13. An earth boring drill bit according to claim 11, wherein said side surfaces of said protuberance are slightly concave. 
     
     
       14. An earth boring drill bit according to claim 11, wherein the axes of said cutter wheels are offset in an angular direction, each said cutter arm nozzle being positioned on a side of its respective said cutter arm opposite from said direction of said angular offset of said cutter wheels.